Data communication networks are oftentimes used to interconnect data systems which use the networks to send and received data. Typically, such data communication networks may comprise ring transmission paths interconnecting ring interface nodes that are used to couple data systems with ring transmission paths. Data is usually transmitted from an originating data system to a ring interface node, oftentimes referred to simple as a node, and over a ring transmission path through intermediate nodes to a node coupled with a receiving data system.
In ring type of data communication networks a node may experience circuit and component failures or a ring transmission path may open thereby causing the network to become inoperative. In the past, attempts have been made to increase the reliability of such types of networks by providing alternative ring transmission paths. Thus, a ring type of data communication network may be designed with ring transmission paths arranged to transmit data in one direction around the network and other ring transmission paths arranged to transmit data in an opposite direction. In the event a node or ring transmission path experiences trouble ones of the ring tranmission paths are looped together at another part of the network to isolate that part of the network experiencing difficulties. A problem arises in these types of data communication networks in that the part of the data communication network that continues in operation generally has no way to communicate with the isolated segment of the network thereby delaying diagnosis of the trouble symptoms and the restoration of the isolated segment to network service.
The foregoing and other problems are solved and a technical advance is achieved by a data communication network arranged to isolate a part of the network experiencing trouble and maintain data communication with the isolated segment to assist in diagnosis and restoral of the isolated segment to network service.